New NDE developments support rapid, economical screening for flow-accelerated corrosion
S. Walker, EPRI NDE Centre, Charlotte, USA
ABSTRACT
New non-destructive evaluation (NDE) equipment is being developed which will aid in detection of flow-accelerated corrosion (FAC) or other wall thickness degradation by reducing the costs associated with the examination. The cost of monitoring piping systems for FAC continues to be an important issue for utility NDE staff. Pipe wall thinning due to FAC has resulted in leaks and ruptures in primary and secondary piping systems when not identified at an early stage. Ultrasonic examination methods are typically used to detect and monitor FAC in electric power generating plants and typically involve a multi-step process. The examination process includes removal of insulation, the layout of an inspection grid, acquisition of thickness measurements, and input of the data into an evaluation program such as Checworks. The evaluation program is typically used for predicting repair maintenance and the appropriate corrective action to take for the particular situation. Insulation removal, disposal and replacement can account for higher costs than the actual NDE, particularly where asbestos insulation is used. As well, grid layout typically constitutes a large portion of the FAC monitoring costs. Several utilities have reported that they spend more time laying out grid patterns than they do acquiring the thickness measurements. The elimination of removing insulation and/or of producing a grid on components prior to examining for FAC can reduce the cost of the inspection by more than 50 %. Two devices to assist utilities with examination of their primary and secondary piping systems for FAC and their service water system piping for wall thinning degradation are currently being developed. The first device is a real-time, digital radiographic examination system which utilises a linear array of solid state detectors, rather than film, to measure wall thickness of insulated or uninsulated piping systems. The second device utilises a personal computer (PC) to generate a virtual grid pattern (which is displayed on the PC screen) along the piping component surface and uses airborne audible sound to locate the transducer position, relative to the virtual grid.
Publication Source: First International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components , 20 - 22 October 1998, Amsterdam, Netherlands. Held by the Joint Research Centre of the European Commission. Publisher:Woodhead Publishing Limited
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